The morning news. [volume] (Savannah, Ga.) 1887-1900, 1887-08-29
ARTESIAN WELLS.
Why Those Located Near the Coast
Are Affected By Tides.

Why Those Located Near the Coast
Are Affected By Tides.
The question of why the flow of water
from artesian wells near the coast increases
as the tide advances, and lessons as it recedes,
has been lately subject for discussion by
several contributors to the Richmond Dis
patch. As there are perhaps hundred ar
tesian wells in this portion of Georgia, in all
of which this popularity has been observed,
the following clear statement of the causes
for it, from an article by Professor G. IL.
Winston, win doubtless prove interesting:
To clear the way may say word as to
artesian wells generally. What is an arte-
sian well! would answer, with no attempt
atprecsion, a deep well generally very deep,
and usually bored, and of small diameterD
in which the water rises, of its own accord,
up to or above the surface. What are the
conditions necessary for such well! As
usually given, they are these; There must
be under the point where the well is to be
bored three strata, parallel to each other,
and having the following characteristics:
l. They must all be concave or bowl
shaped; and the point for the well must be
somewhere in the hollow of the bowl, but
at a much lower elevation than the upper
edges of the bowl.
The upper stratum, which we will call No
!, and the lowest. which we will call No. 3,
must both be impervious, or able to hold
water
Between these two impervious strata must
be one of sand or gravel, or loose-textured
rock, into and through which water can
somewhat freely pass. Call this No. 2
These strata may be few miles or hundreds
of miles in extent, and may be few feet or
thousands of feet in thickness, and may have
much irregularity of thickness, form and
structure, ETC., but must be substantially as
have stated. Nor must it be thought that
such special arrangement of strata must
necessarily be rare: for we have here in
Richmond many alternate pervious and i'm
pervious strata. and to this alienation all
our springs are due.
Now as the rain falls on the exposed edge
or outcrop of No. 2 (which edge all around
may be hundreds of square miles in extent,
it settles down between No. l and No. 3
(neither of which will permit it to pass,
and fills up and saturates completely the
porous No. 2, with veins and channels here
and there perhaps. Suppose, now, some one
living in the hollow of this double-bottomed
bowl bores down till he gets through the
hard No. |, and strikes the porous No. 2, it
is clear that the pressure of the water, which
fills up the bowl to its edges, will force up
stream through the boring as high theo-
retically) as those edges themselves are; just
as the fountain on the square might be ex-
pected to rise as high as the level of the res
ervoir. Permit me to give an Illustration
that | have often used Take a basin or
deep plate-this is No. 3; fill even full with
sand-this is No. 2; press far down into the
sand deep saucer of earth-this is No /.
Pour water on the exposed edges of the sand
till it is saturated. Now imagine a hole
bored through the earth in the saucer, but
not through the saucer; that would be an
ordinary well. But let the hole go down
through the saucer, and that would be an
artesian well, and If piped the water should
rise in it nearly up to the height OF the sand.
But to our problem, why do the West
Point wells ebb and flow with the tide"
suppose these wells and Others on the Allan
tic coast are bored, not on three bowl-shaped
strata, but on strata that simply incline to
wards the ocean, and that the ocean itself
forms the western side of the bowl. Our
Richmond granite may be the No, 3 to hold
the water for the West Point wells, and the
rain falling on this flows slowly down it into
the ocean under some No. u, discharging
itself, perhaps at a great depth, and flowing
only by the difference of level between it's
starting point at the upper edge of the
stratum and level of the ocean.
We must have the idea then, of the water
bearing stratum No. 9, abuttiug deep down
against the ocean, into which it slowly pours
its waters, while more water comes in stead
lily from the higher part of the slope on the
east; and that at West Point there Is an up
ward pressure on the everything No. due to
the combined effect of the height of the
water in No. OH the east and the level of
the ocean on the west. This pressure causes
the water to rise in the West Point wells.
Now let the ocean level rise-say four feet
with the tide; the upward pressure at West
Point and elsewhere rises also, and more
water flows from the wells, and uice versa
as the tide recedes. To illustrate further.
take U-shaped tube and let one leg-say
the right-be flexible Bore O hole in the
hollow of the and insert a fine glass tube
as gauge. Let water run in the right side
to keep IL full while it runs out Of the right
flexible side. Now raise and lower this
flexible side Tor better, let the flexible tube
dip into cup of water, and then raise and
lower this cup, and the water will rise and
fall in the gauge tube accordingly.
The application is easy: The left leg is
the slipping No. 2 entubed between l and 3.
The small gauge tube is the well; and the
right flexible leg Tor the cup of water the
ocean. The raising and lowering of this
leg Tor the cup answer to the tides, and
the rising and falling of the level in the
gauge is the cbbing and flowing of the wells,
which respond to them.